The origin and development of the immune system with a view to stem cell therapy

How cell migration helps immune sentinels

The immune system relies on the migratory capacity of its cellular components, which must be mobile in order to defend the host from invading micro-organisms or malignant cells. This applies in particular to immune sentinels from the myeloid lineage, i.e. macrophages and dendritic cells. Cell migration is already at work during mammalian early development, when myeloid cell precursors migrate from the yolk sac, an extra embryonic structure, to colonize tissues and form the pool of tissue-resident macrophages. Later, this is accompanied by a migration wave of precursors and monocytes from the bone marrow to secondary lymphoid organs and the peripheral tissues. They differentiate into DCs and monocyte-derived macrophages. During adult life, cell migration endows immune cells with the ability to patrol their environment as well as to circulate between peripheral tissues and lymphoid organs. Hence migration of immune cells is key to building an efficient defense system for an organism. In this review, we will describe how cell migratory capacity regulates the various stages in the life of myeloid cells from development to tissue patrolling, and migration to lymph nodes. We will focus on the role of the actin cytoskeletal machinery and its regulators, and how it contributes to the establishment and function of the immune system.

miR-145-5p Increases Osteoclast Numbers In Vitro and Aggravates Bone Erosion in Collagen-Induced Arthritis by Targeting Osteoprotegerin

BACKGROUND Osteoprotegerin (OPG) inhibits bone resorption and binds with strong affinity to receptor activator of NF κB ligand (RANKL), thereby preventing RANKL from binding to its receptor RANK. Osteoclasts have documented effects on bone erosion of rheumatoid arthritis (RA). The aim of this study was to examine the role of miR-145-5p in the regulation of RA osteoclast differentiation and bone erosion. MATERIAL AND METHODS Expression of microRNA-145-5p in human peripheral blood mononuclear cells (PBMC) and synovial tissue was assayed by real-time polymerase chain reaction (RT-PCR). OPG, RANK, and RANKL expression in RAW-264.7 cells was examined by RT-PCR and Western blot analysis. Osteoclast formation was detected by tartrate-resistant acid phosphatase (TRAP) staining. The effect of miR-145-5p on predicted target mRNAs was examined by luciferase reporter assays. Collagen-induced arthritis (CIA) was induced by injecting DBA/1 mice with bovine type II collagen (CII), and miR-145-5p agomir was administered by intravenous injection. Morphological changes in the CIA joint were assessed by micro-computed tomography (CT) and histopathology. RESULTS miR-145-5p levels significantly increased in RA PBMC and synovial tissue compared with normal PBMC and osteoarthritis (OA) tissue. After transfection of RAW-264.7 cells with miR-145-5p, RANK and RANKL expression increased significantly, while OPG expression decreased significantly. TRAP staining results showed osteoclast numbers increased. Micro-CT analysis of the arthritic joints showed that the miR-145-5p agomir caused bone erosion in mice, and histopathological analysis revealed that miR-145-5p agomir aggravates cartilage erosion. CONCLUSIONS Our findings indicate that administration of miR-145-5p aggravates joint erosion in CIA mice. This suggests that miR-145-5p is a potential target for the treatment of RA.

Swertiamarin, a natural steroid, prevent bone erosion by modulating RANKL/RANK/OPG signaling

Bone erosion is a central feature of rheumatoid arthritis (RA) that is characterized by the infiltration of the synovial lining by osteoclasts and lymphocytes. In the present study, swertiamarin a major secoiridoid glycoside was evaluated for anti-osteoclastogenic property to prevent bone erosion in Freund's complete adjuvant (FCA) induced in-vivo model, in-vitro osteoblast and osteoclasts as well as in co-culture system and in-silico molecular docking analysis. The swertiamarin treatment decreased the expression of TRAP, RANKL, and RANK levels and increased the levels of OPG levels significantly in both in vitro and in vivo models. In in vitro, the compound treatment significantly increased the cell proliferation and ALP levels in osteoblast cells; the high proliferation (153.8600±5.23%) and ALP release (165.6033±4.13%) were observed at 50μg/ml concentration of swertiamarin treatment. At the same time the treatment decreased the TRAP positive cells in osteoclast cells; the high reductions of TRAP positive cells (39.32±3.19%) were observed at 50μg/ml of swertiamarin treatment. The treatment modulated the levels of pro-inflammatory cytokines, MMPs and NF-κB levels in osteoblast and osteoclast co-culture system. In in silico analysis swertiamarin had affinity towards the proteins RANK, RANKL and OPG residues with low binding energy -4.5, -3.92 and -5.77kcal/mol respectively. Thus, the results of this study revealed the anti-osteoclastogenic activity of swertiamarin on the prevention of bone destruction.

Correspondence on: A Hyaluronic Acid-Rich Node and Duct System in Which Pluripotent Adult Stem Cells Circulate

The origin of the wide spread node and duct system described by Rai et al. remains a mystery. The explanation came when another study on yolk sack hemopoiesis was compared with the "primo vascular system". It came out that the yolk sack hematogenic tissue, introduced to the embryo by the vitelline veins, does not disappear in adults, but continues to exist in form of nods and ducts along blood vessels and different organs.

Recruited peripheral blood monocytes participate in the liver extramedullary hematopoietic milieu

The hematopoietic microenvironment has been investigated and well defined in the bone marrow. However, there is a lack of studies on the extramedullary hematopoietic milieu such as in the liver, to which hematopoietic stem cells migrate and there commence hematopoiesis under pathological conditions such as bone marrow failure. We induced extramedullary hematopoiesis by phenylhydrazine in the adult mouse liver and investigated the immunohistochemical, ultrastructural, and molecular changes within this organ. Using an intravital lectin injection technique, we found numerous monocytes attached to the central vein prior to hematopoietic foci formation. These cells were later incorporated into the hematopoietic foci. An increase in the mRNA expressions of the monocyte attracting chemokine CCL-2 (MCP-1) was noted in the central vein region as well as in cells within the hematopoietic foci. Together with local liver components, we regard these monocytes as components of the extramedullary hematopoietic milieu. We conclude that the recruitment of extra-hepatic monocytes is an important event during extramedullary hematopoiesis in the liver and that these monocytes participate in the liver hematopoietic microenvironment.

Neuropathogenesis of congenital cytomegalovirus infection: disease mechanisms and prospects for intervention

Congenital cytomegalovirus (CMV) infection is the leading infectious cause of mental retardation and hearing loss in the developed world. In recent years, there has been an improved understanding of the epidemiology, pathogenesis, and long-term disabilities associated with CMV infection. In this review, current concepts regarding the pathogenesis of neurological injury caused by CMV infections acquired by the developing fetus are summarized. The pathogenesis of CMV-induced disabilities is considered in the context of the epidemiology of CMV infection in pregnant women and newborn infants, and the clinical manifestations of brain injury are reviewed. The prospects for intervention, including antiviral therapies and vaccines, are summarized. Priorities for future research are suggested to improve the understanding of this common and disabling illness of infancy.

Expression of the hematopoietic stem cell antigen Sca-1 (LY-6A/E) in liver sinusoidal endothelial cells: possible function of Sca-1 in endothelial cells

Several reports have shown that the expression of Sca-1 (Ly-6A/E), the most widely used murine hematopoietic stem cell marker, is restricted to blood vessels in several nonhematopoietic tissues. However, there is no information about which components are expressing Sca-1, and what the role of Sca-1 could be. Because we have previously shown that murine liver endothelial cells from the hepatic sinusoid (LSEC) express some HSC markers (i. e., CD34 and c-kit), we hypothesized that these cells could also express Sca-1. In this work, we show that Sca-1 is constitutively expressed in LSEC, as well as in the liver sinusoid lumen. The expression of Sca-1 in LSEC was confirmed at the mRNA and protein level by reverse transcriptase (RT)-PCR, flow cytometry, and immunofluorescence studies. The expression of Sca-1 was enhanced on the surface of LSEC by tumor necrosis factor (TNF). We examined whether Sca-1 ligation on the surface of LSEC regulates some biological response in these cells. Our results show that ligation of Sca-1 by the anti-Ly-6A/E monoclonal antibody (mAb) D7 stimulated the growth of LSEC and the production of interleukin-6 (IL-6) by these cells. To our knowledge, this is the first report that LSEC express Sca-1, which may constitute additional support to the theory of a common progenitor for the hematopoietic and endothelial cells. Our results show a novel role of Sca-1, indicating that it induces activation of LSEC to proliferate and to produce IL-6. These results suggest that Sca-1 may participate in several clinical conditions such as angiogenesis and inflammation.

Commentary: the role of cell migration in the ontogeny of the lymphoid system

The foundations of experimental hematology were laid by histologists, and while their contributions were enormous, they were limited in their interpretation of very dynamic processes by the static nature of the methodology. The middle of the twentieth century saw the introduction of techniques for hematopoietic cell marking and development of in vitro and in vivo assays for primitive hematopoietic cells, allowing dynamic studies of hematopoiesis. Paralleling this was an understanding of cellular immunology with the discovery of the role of the thymus and the identification of T and B lymphocyte lineages. In the 1960s a series of ontogenetic studies in birds and subsequently in mice revealed that hematopoietic and lymphoid development involved migration streams of primitive cells that colonized developing primary lymphoid organs as well as spleen, marrow, and liver. The yolk sac was proposed as the ultimate origin of these lympho-hematopoietic precursors. Subsequent studies identified a region associated with the dorsal aorta as the primary site of "definitive" stem cells. These opposing views are currently achieving a compromise that recognizes that both sites contribute stem cells involved in seeding the developing tissues. The clear distinction between the local origin of the inducing microenvironment provided by the endoderm or by stroma derived from mesenchymal stem cells of mesodermal origin, and the immigrant origin of the hematopoietic stem cells and progenitors, raises intriguing questions in the current climate of stem cell plasticity, cell fusion, and discovery of stem cells in adult marrow with the capacity to generate hematopoiesis as well as other mesodermal, ectodermal, and endodermal lineages.